^{page 66 note a} Notes on the Decay of Glass, especially upon that of the Ancient Glass found at Nineveh, Appendix to Layard, Second Expedition, 1853; and On the Decomposed Glass found at Nineveh and other places, Transactions of the British Association, 1860, p.9. Both are important communications, and should beread carefully in connection with this subject. Itso happens that my illustrative example No. 9 camefrom a specimen formerly in the possession of Sir David Brewster, and greatly prized by him at a time when specimens of Roman glass were much more difficult to procure than at present. Having noticed the windows of stables often coated with a precisely similar iridescence (Ex. 13), and conjecturing it was caused by ammoniacal fumes, he formed the idea that the glass might have been buried near a Romanstable, and thus acted upon by the decomposing excretions of the horses. Sir David himself scraped off some of the films, and gave them as a curiosity, with the preceding explanation, to the Reverend H.G. W. Aubrey, of Hale Rectory, Salisbury, at that time a neighbour in Scotland, who had the kindnessto present them to me.

^{page 67 note a} Bernard Palissy, writing in 1563, says the glaziers in Poitou andBretagne attributed the decay of their church-windows to the moon.

^{page 67 note b} This view was advocated by at least one of the speakers in the discussion which followed the reading of this Paper.

^{page 67 note c} “A diminutive moss or lichen, which absolutely decompounds the substance of the glass in vermicular lines.” , Whitaker, Loidis and Eltnete, ii. 322, note. See alsoGoogle Scholar, Winston, Inquiry, & 1867, i. 23Google Scholar.

^{page 68 note a} In the British Museum there is a large quantity of ancient iridescent glass, collected by Mr. Layard in Mesopotamia, and believed to be Assyrian; but it is probable that most of the specimens are of the Eoman period, derived from the Eoman colony Niniva Claudiopolis, which occupied the site of ancient Nineveh. A similar difficulty occurs with respect to the fragments of iridescent glass found by Captain Warren in his excavations at Jerusalem. It is impossible to say where the specimens thus discovered were manufactured.

^{page 68 note b} There are several Eoman pastes in the British Museum which show iridescent decay.

^{page 68 note c} Though, strangely enough, there was a proposal in The Field newspaper, 23 Dec. 1876, to manure soils poor in silica with broken glass.

^{page 69 note a} These numbers refer throughout to the illustrative examples, of which a list will be found appended.

^{page 69 note b} I have avoided defining what takes place more precisely, because I have not myself been able to observe more. Sir David Brewster describes the gradual formation of “hemispherical cups” of films, like nests of watch-glasses, answering to what I have described as blisters. I have not been able to verify these observations, nor the appearance as “of the section of a pearl or of an onion.” Anything advanced by so careful and skilled an observer as Sir David is nevertheless of importance; and I would again refer the reader to a careful perusal of his papers. At the same time I must confess that it is not quite easy at all times to be certain how far he is describing what he himself actually saw, or his inferences from what he saw. That he is distinctly wrong in stating that the films are still glass and not silica arising from the decomposition of glass, is proved by the analyses which will be given hereafter.

^{page 73 note a} An unpractised eye would certainly mistake these lines for scratches, and at once conclude them to be so. By the microscope, however, they are readily distinguished; for, whilst the edges of the finest scratch are always rough and irregular, from the chipping off of particles conchoidally on either side, the strise, whether left in relief or corroded, always have a smooth, even if it be an irregular, outline.

^{page 75 note a} “Vitrum putrefactibilium ultimum, in aere manet velut seternum. Sepultum vero post annos, fra-cedinem admittit, crusta obvolvitur, sal ejus dissolutum, fatiscit: et arena sui constitutiva permanet.” Helmont, Van, Opera, edit. 1667, 95, § 15Google Scholar.

^{page 77 note a} There is a mode of decay referred to by Knapp (Chemical Technology, ii. 8) and various other writers, on the authority of Colladon (Journal de Chimie Medicate, Paris, xx. 258), which I have not described, because I have not myself seen it. Some pieces of glass were found in “an old pit twelve feet deep, both flexible and so soft that they could be kneaded and cut with a knife, but which regained their hardness and frangibility by exposure for several hours to the air.” Can such a tradition have originated in the fact that Roman and other bottles and jars dug up are often bulged and indented (from original faults in their manufacture), supplemented by the imagination that the bulging and indentation was done when they were dug out, and that they subsequently hardened again?

^{page 77 note b} There is in the Guide to the British Museum an excellent notice of the glass by Augustus W. Franks, Esq. F.K.S. F.S.A. and the sumptuous Catalogue of the Sladeglass, with Introduction by Alexander Nesbitt, Esq. F.S.A. is, of course, invaluable. The writer regrets however that he has never had an opportunity of carefully studying the latter (which was privately printed and very limited in number), though he is indebted to R. H. Soden Smith, Esq. the Librarianof the South Kensington Museum, for having once had the opportunity of looking it over. The forthcoming Catalogue of Glass at South Kensington, also by Mr. Nesbitt, is sure to be a valuable as well as an easily accessible volume.

^{page 78 note a} Bodies are said to be opaque, when they allow neither light nor objects to be discerned through them; translucent, when they allow light to be discerned through them bnt not objects; transparent, when they allow both light and objects to be discerned through them.

^{page 78 note b} Glass is here called porcellaneous, horny, or crystalline, from its resemblance to porcelain, horn, or crystal, in appearance. How closely the ancient opaque glass resembles porcelain, is shown by the fact that in the early hand-catalogues of the BritishMuseum many of the vases now known and described as of “opaque glass”are described as being of “porcelain or opaque glass,” it being doubtful which of the two they were. That they were really glass was eventually proved, however, by the appearance of fractured specimens, and by some of the vases being found to be not so opaque as others. The translucent makes of glass very closely resembled horn, cut about as thin as that formerly used for lanthorns, but not so thin as that for horn-books. Pliny compares the Boman glass to crystal—“proxima crystalli similitudine ” (Hist. Nat. xxxvi. 67. The Greeks used the same word (ΚρúoTªλλος) both for (their transparent) glass, ice, and crystal. Crystal was indeed supposed to be ice, congealed by so intense a cold that it was impossible to thaw it.

^{page 79 note a} Primitive Man, Eng. edit. 1870, p. 261.

^{page 79 note b} “Hesiod, who is supposed to have written about 900 B.C., and who is the earliest European author whose works have come down to us, appears to have lived durin gthe transition between the Bronze and Iron ages … speaking of those who were ancient, even in his day, he says that they used bronze, and not iron … The Trojan war also took place during the period of transition.” (Sir Lubbock, John, , Bart., Prehistoric Times, p. 5.)Google Scholar There are occasional references to the use of iron of much earlier date, in the Pentateuch, for instance, but it cannot be inferred from these that the use was at all general.

^{page 80 note a} Sir J. G. Wilkinson, in Rawlinson's Herodotus, App. Book II.ch. viii. p. 345.

^{page 80 note b} Sir Wilkinson, J. G., Ancient Egyptians, iii. 88.Google Scholar

^{page 80 note c} Notice Historique de l‘Art de la Verrerie né en Egypte, Description de l'Egypte, II. iii. 2.

^{page 80 note d} Recherches Philosophiques, p. 304.

^{page 80 note e} , Kenrick, Phoenicia, 57, 61, 340. “Broadly speaking, we may begin to date Phoenician history from the time when Sidon first assumed the rule, or about 1500 B.C.” Deutsch, in Kitto, Cyclop. Bibl. Lit. s.v. Phoenicia).Google Scholar

^{page 81 note a} , Kenrick, op. cit. 297Google Scholar.

^{page 81 note b} id. 229.

^{page 81 note c} Herodotus, I. i.

^{page 81 note d} Deutsch. loc. cit.

^{page 81 note e} Hist. Nat. xxxvi. 65. “…Quibus accensis permixta arena litoris, translucentes novi liquoris fluxisse rivos, et lianc fuisse originemvitri.” The expression in italics is interesting, as showing that Pliny took for granted that the first glass made was as transparent as that of his own day.

^{page 81 note f} The Egyptian nitre-pits (i.e. natron, or soda pits, pits containing native carbonate of soda), and artificial nitre works, were the most famous of the ancient world. For Pliny's description of them see op. cit. xxxi. 46. The ruins of glass furnaces are still seen at the natron lakes. Sir J. G. Wilkinson, note 8, to Eawlinson's Herodotus, ii. 44.

^{page 81 note g} Slade Collection of Glass, Guide to Brit. Mus. p. 117.

^{page 81 note h} Birch, Dr., Egyptian Antiquities, Guide to Brit. Mus. p. 119.Google Scholar

^{page 81 note i} There are many fine specimens in the British Museum, from Camirusin Rhodes, claimed as Phoenician by so high an authority as Mr. C. T. Newton.

^{page 81 note j} In the British Museum there are some fragments of such Phoenicianvases of opaque glass from the temple of Athor, at the Sarabut-el-Khadem, in the peninsula of Sinai. It is not impossible that these precious remains may be part of the spoil of the Egyptians, carried there by the children of Israel.

^{page 82 note a} Odyss. xv. 416; and comp. Herodotus, I. i.

^{page 82 note b} And yet, as Herodotus says (ii. 104), “The Syrians of Palestine themselves confess that they learnt the custom (of circumcision) from the Egyptians.” Compare our Lord's statement (John vii. 22). “Moses therefore gave you circumcision, not because it is of Moses, but of the fathers.”

^c , Michaelis, Hist. Vitri apud Hebraeos, in Comment. Soc. Begiae scientiarum Gottingensis, torn. iv. p. 301.Google Scholar

^{page 82 note d} See for instance , Kenrick, op. cit. 63.Google Scholar

^{page 82 note e} Deut. xxxiii. 19; with which compare Gen. xlix. 13.

^{page 82 note f} 1 Kings v. 1, 7, & ix. 10–14, 26–28; xi. 1–8.

^{page 82 note g} 1 Kings vii. 14; 2 Chron. ii. 14.

^{page 82 note h} 1 Kings v. 11; 2 Chron. ii. 10; with which compare Acts xii. 10, and , Josephus, Antiq, viii. 2, 7; see alsoGoogle Scholar, Kenrick, op. cit. 355Google Scholar.

^{page 82 note i} 2 Sam. v. 11; 1 Chron. xiv. 1.

^{page 82 note k} 1 Kings v.; 1 Kings vii.; 1 Chron. xxii. 4.

^{page 83 note a} , Thurnam, Ancient British Barrows, Archseologia, XLIII. 499.Google Scholar

^{page 83 note b} , Rawlinson, Herodotus, App. bk. II. ch. v. p. 317.Google Scholar

^{page 83 note c} 1 Kings vii. 14.

^{page 83 note d} 2 Chron. ii. 7.

^{page 83 note e} Strabo, Geog. lib. xvi. cap. ii. sec. 25; Josephus, Bel. Jud. ii. 9.

^{page 84 note a} The only arguments with which I am acquainted in favour of an earlier existence of translucent glass among the Egyptians are as follows: 1. It is said that bottles containing red wine are represented in some of the earliest paintings; and it has been inferred hence that the glass of which they consisted must have been transparent. This, however, does not by any means follow; since wine could scarcely have been represented in an opaque bottle without making the bottle appear transparent, whether it were actually so or not. 2. A bead of circa B.C. 1450, mentioned by Sir J. G. Wilkinson, described by some as “transparent,” was formerly believed to be glass. This, however, is now considered by Professor Maskelyne to be obsidian.

^{page 84 note b} Nat. Hist. xxxvi. 66Google Scholar.

_{page 84 note c} Herodotus, ii. 44. It is scarcely worth while to refer to the mirrors (probably of Phoenician origin) mentioned by Isaiah (iii. 23), because it is impossible to ascertain from the Hebrew text whether they were of glass or metal, or if glass, of what kind.

^{page 84 note c} De Lapidibus, pp. 395, 396.

^{page 84 note e} Op. cit. xxxvii. 5.

^{page 85 note a} Kenrick, op. cit.

^{page 85 note b} Clementine Becognitions, vii. 12Google Scholar.

^{page 85 note c} , Theophrastus, cited by , Pliny, op. cit. xxxvii. 5.Google Scholar

^{page 85 note d} Same writer, cited by same, loc. cit.

^{page 85 note e} Apion, surnamed Plistonices, cited by , Pliny, op. cit. xxxvii. 5.Google Scholar

^{page 85 note f} , Franks, op. cit. p. 118.Google Scholar

^{page 85 note e} , Rawlinson, Ancient Monarchies, i. 308, 309, 347, 500.Google Scholar

^{page 85 note h} The question is argued, with much learning, by , RawKnson, op. cit. ii. 535,Google Scholar and Herodotus, App. book i. essay vii.

^{page 86 note a} , Layard, Nineveh and Babylon, pp. 503, 507Google Scholar; , Eich, First Memoir, p. 29Google Scholar; Porter, Ker, Travels, ii. 392Google Scholar.

^{page 86 note b} , Rawlinson, op. cit. iii. 413.Google Scholar

^{page 86 note c} , Rawlinson, Herodotus, Introduct. ch. ii. p.59.Google Scholar

^{page 86 note d} Gesenius, a high authority, thinks it does, and refers to Michaelis, in Comment. Soc. Gotting. and Hambergeri, Hist. Vitri ex antiquitate eruta,ibid.See also Dr. J. E. Beard, in Kitto, Cyclop. Bibl. Lit. s. v. Glass.

^{page 86 note e} , Kenrick, op. cit. p. 201.Google Scholar

^{page 86 note f} The question is discussed, with great learning, in Ancient Monarchies, i. 459, 460Google Scholar.

^{page 87 note a} Deutsch. op. cit. s. v. Phœnicia.

^{page 87 note b} Herodotus, v. 58. See also Rawlinson's note to same, and App. book ii. chap. v. pp. 317, 318, &

^{page 87 note c} , Kenrick, op. cit. p. 98.Google Scholar

^{page 87 note d} Herodotus, ii. 49, 50.

^{page 87 note e} Ancient Egyptians, 2nd ser. i. 148. “Almost all the names of the gods came into Greece from Egypt. …[with certain exceptions]. The othergods have been known from time immemorial in Egypt.” Herodotus, ii. 50. See also Sir Gardner Wilkinson's Essay in Rawlinson's Herodotus, App. book ii. chap. iii.

^{page 87 note f} Ancient Egyptians, 2nd ser. i. 168, quoting Herodotus, ii.51.

^{page 887 note g} Op. cit. 2nd ser. i. 147; 2nd ser. ii. 320.

^{page 87 note h} Op. cit. 2nd ser. ii. 320.

^{page 87 note i} Op. cit. 2nd ser. ii. 320, quoting Herodotus, ii. 171.

^{page 87 note j} Op. cit. i.156.

^{page 87 note k} Op. cit. iii. 310.

^{page 88 note a} Herodotus, ii. 69.

^{page 88 note b} Herodotus (iii. 24), speaking of the embalmed Ethiopians, says they were put in glass (ϋαλος), but, from the context, this must have been talc, or lapis specularis.

^{page 88 note c} Nubes, Act 2, sc. i. A stone beautiful and transparent is mentioned, used to kindle fire; but this may have been rock crystal.

^{page 88 note d} That used by the Phoenicians. The river was supposed to spring from the lake of Cendevia, at the foot of Mount Carmel, between Phoenicia and Judsea, emptying itself into the sea near Ptolemais. , Pliny, op. cit. xxxvi. 26.Google Scholar

^{page 88 note c} “…Vitreâte Fucinus undâ Te liquidi flevere lacus.” Æneid, vii. 759.

^{page 88 note f} “Perlucidior vitro.” Carm. ii. Ode 2. “Splendidior vitro.” Carm. iii. Ode 3.

^{page 88 note g} Op. cit. xxxvi. “Maximus tamen honos in candido translucentibus, quam proxima crystalli similitudine.”

^{page 88 note h} Op. cit. xxxvi. 66.

^{page 88 note i} Lib. xvi. cap. ii. sec. 25.

^{page 89 note a} Pellatt, Apsley, Curiosities of Glass-making, p. 20. The date of this marvellous vase is uncertain, but it was found in a sarcophagus, believed to be that of the Emperor Alexander Severus, killed A.D. 325.Google Scholar

^{page 89 note b} Op. cit. xxxvii. 22.

^{page 89 note c} Id. 26.

^{page 89 note d} Id. 37.

^{page 89 note e} Id.xxxvi. 67. See also xxxvii. 65, 66, for more respecting counterfeit stones and how to distinguish them; and Sir Wilkinson, Gardner, op. cit. iii. 93Google Scholar.

^{page 89 note f} Sir Wilkinson, Gardner, op. cit. iii. 92. For an interesting reference to the Alexandrian glass-works, see Strabo, xvi. ii. 25.Google Scholar

^{page 89 note e} Sir Wilkinson, Gardner, op. cit. iii. 93,Google ScholarVopiscus, quoting, Vita Saturnini, c. 8Google Scholar.

^{page 89 note h} Op. cit. xxxvi. 66.

^{page 90 note a} On the supposed discovery of a Roman glass manufactory near Brighton, by Guest, Dr., see , Wright, Celt, Roman, and Saxon, 1861, p. 229; and on similar remains inGoogle Scholar, France, , Peligot, Le Verre, 329, 330Google Scholar.

^{page 90 note b} See Lindenschmit, Das Germanische Todtenlager hei Selzen, Mainz. 1848.

^{page 90 note c} Etymologiarum, xvi. 15Google Scholar.

^{page 91 note a} , Bede, Hist. Abbatum Wiremuth et Gyrvensium, Smith's edit. 295. 3.Google Scholar

^{page 91 note b} Rot. Parl. i. 228Google Scholar, cited by A. Nesbitt, F.S.A., Slade Cat. Introd. p. xxxii.

^{page 91 note c} Dugdale, Antiq. Warwickshire, edit. 1656.

^{page 91 note d} Linas, Engraved in De, Orfévrerie cloisonnée, Paris, 1877, torn i. pl. v. bis.Google Scholar

^{page 91 note e} Voyage en Perse, Amst. 1711, t. iv. p. 258.

^{page 91 note f} , Kenrick, Phœnicia, 395.Google Scholar

^{page 92 note a} On the flourishing condition of the Sidonian glass-works under the Eomans, in the first century A.D., see Pliny, loc. cit.

^{page 92 note b} Kenrick, op. cit. 444.

^{page 92 note c} Surah, xxvii. quoted by , Michaelis, op. cit. § 10, p. 333Google Scholar.

^{page 92 note d} , Kenrick, op. cit. p. 444.Google Scholar

^{page 92 note e} Several references to French inventories are given by , Labarte, Hist, des Arts Industriels au Moyen Age, v. 538Google Scholar.

^{page 93 note a} Confirmed by Edrisi, i. 349, who states that both very fine glassand earthenware were made there.

^{page 93 note b} De Coloribus, iii. 49. As Theophilus, whose work is thought to belong to the tenth or eleventh century, mentions Heraclius, and the latter cites Isidore of Seville, who lived in the seventh century, the treatise of Heraclius must be placed between those two dates.

^{page 93 note c} , Labarte, Hist, lies Arts Industriels au Moyen Age, edit. 1866, iv. 538.Google Scholar

^{page 93 note d} Hist. Ecclesiast. iv. 35. The account is repeated by Tours, Gregory of, De Gloria Martyrwn, i. 10Google Scholar.

^{page 93 note e} De Ceremoniis Aulce Byzantinae, ii. 44, edit. Reiskii, i. 661.

^{page 93 note f} , Labarte, op. cit. 539.Google Scholar

^{page 93 note g} ύéμίακλεοπτ. The Editor has translated this, as he says—“ut aliquid darem nonprorsus alienum,” vitra Heliopolitana; but confesses that it is impossible to be certainas to the meaning of the manuscript.

^{page 94 note a} Diversarum Artium Schedula, ii. 13, 14, 15, 16.

^{page 94 note b} See also , Csesar, De Bello Gallico, iii. 13; and Strabo, i. 195.Google Scholar

^{page 94 note c} , Giustiniani, De Translatione, etc. lib. 2Google Scholar; , Michieli, Feste Veneziane, i. pp. 96–100;Google ScholarDanduli, AndreaeChronicon, viii. i. 27Google Scholar; Navagero, Storia della Republ. Venez. ann. 819.

^{page 94 note d} , Hazlitt, Hist, of Venice, i. 183, 247, 324,331; ii. 23, 99.Google Scholar

^{page 94 note e} And. , Danduli, Chron. ix. xii. 10.Google Scholar

^{page 94 note e} And. , Danduli, x. viii. 10.Google Scholar

^{page 94 note f} Id.id.11.

^{page 95 note a} And. Danduli, x viii. 10, note(ann. 1275).

^{page 95 b} , Hazlitt, op. cit. i. 62, 311, 323, and passim.Google Scholar

^{page 95 note c} Ricerche Storico-critiche, etc. 187. See also p. 188, where he says the Venetians learned the art of making mirrors from the Greeks, citing Muratori, Dissertationes Ital. torn ii.

^{page 95 note d} “— Massaeque fiunt. Postea ex massis rursus funditur in officinis, etc.” De Coloribus, etc. iii. 5.

^{page 95 note e} Bacon, in a passage I do not remember to have seen quoted, says that the ashes of an herb, called by the Arabs Kail (kali), growing in the desert between Alexandria and Eosetta, were compressed into masses like stones, and sold to the Venetians for making glass (Nat. Hist. viii. 770Google Scholar). His authority was probably Sandys, who travelled in 1610, and says—“In the desert between Alexandria and Cairo is a weed called Kali by the Arabs, which they use for fuel and sell the ashes, crushed together like a stone, in great quantity to the Venetians, who, equally mixing the same with the stone brought from Pavia by the Ticino, make thereof their crystallineglass.” Neri, who gives much information on the materials used by the Venetians, says (1612) the alkali brought from Syria or the Levant was called Rochetta, and was the ash of a plant which grew there in abundance. It was elaborately purified before use; and the greatest care also was taken in the choice of a pure form of silica. Al-hilyn is described in Kazimirski's Arabic Lexicon as “Cendres des plantes alcalines;” derived from the verb Kalai to burn; Kalah, in Hebrew, is to burn, roast, parch; hence Kali, roasted or parched grain (Lev. xxiii. 14; Euth ii. 14).

^{page 96 note a} Carlo Marino, Storia civile e politica del Commercio de' Veneziani, i. ii. 213; v. ii. 258; and Filiasi, Saggio sull' Antico Commercio de' Veneziani, II. vi. 147.

^{page 96 note b} Storia filosophica, etc. ii. 35, 36Google Scholar.

^{page 96 note c} “Noi vi abbiamo contato dei maestri barbieri ed appresso viconteremo dei maestri vetrai, quelli che fanno i lavori ed i lavorietti di vetro.” Canale, Da, Cronaca Veneta, cclxxxi. ann. 1268Google Scholar.

^{page 96 note d} “Captum, quod de cetero Vitreum, Alumen, Sablonum, seu alia, de quibus vitreum fieri debeat, non possint portari extra terram, nee de eis possit fieri sigillum sine lieentia data a Duce, et Consilio Majore, sub poena perdendi ea quae portarentur.” Danduli, Chron. X. ix.

^{page 96 note e} , Filiasi, Ricerche, etc. 187.Google Scholar

^{page 96 note f} Id.id.

^{page 96 note g} Sabellici, Cocci, De Venetae Urbis Situ, lib. 3.Google Scholar

^{page 96 note h} Filiasi, Ricerche, etc. 189. “Atqui omnium gentium haec oculis maritima subjicere negotia.” Sabellici op. cit.

^{pge 97 note a} , Bussolin, Guida alle fabbriche di Murano, 1842, p. 62.Google Scholar

^{page 97 note b} , Peligot, Le Verre1, p. 342.Google Scholar

^{page 97 note c} Id. 343.

^{page 97 note d} Id. 344, Labarte, op. cit. 1875, iii. 396.

^{page 98 note a} , Labarte, op. cit. iv. 592.Google Scholar

^{page 98 note b} Kunckel's translation and notes on Neri and Merret, describing the purest sources of silica and mode of purifying the alkalies, and reviewing all that was then known on the subject, was published at Frankfort in 1689.

^{page 98 note c} , Labarte, op. cit. iv. 595.Google Scholar

^{page 98 note d} , Pennant, London, 5th edit. p. 377.Google Scholar

^{page 98 note e} Turner, Hudson, Domestic Architecture, i. 76–79, quoting Lansdown MS. No. 59, art. 72 and 76.Google Scholar

^{page 98 note i} Voyages, edit. 1809, i. 496.

^{page 99 note a} , Knapp, Chemical Technology, ii. 2.Google Scholar

^{page 99 note b} By this word, here and elsewhere, I mean—perceptibly to thenaked eye.

^{page 100 note a} This should be considered by writers who, like M. Peligot (Verre,-p. 55), attribute to natural decay the disappearance of almost all windows anterior to the twelfth century in date. It is extremely rare to find a pane eaten completely through (Ex. 57), and especially so during the earlier centuries, in which the glass was generally extremely thick (Ex. 108).

^{page 103 note a} Of beech-wood, crude and unpurified (, Theoph. Div. Art. Sclied. II. i. 4); of dried grass and fernGoogle Scholar (, Vino. , Bellov. Spec. Nat. vii. 78)Google Scholar; of fern and beech, two of fern and one of beech (Heraclius, iii. 7). “Who wold wene it possible y^t glasse were made of feme royts.” ( Workes of Sir Thomas More, Knyght, fol. 1557, p. 126.) “Of the Glass we use, the purest is made of the ashes of Chali or Glasswort and the coarser or green sort of the ashes of Brake and other plants.” (Sir Brown, Thomas, Vulgar Errors, ii. 3.)Google Scholar “Ashes of Chali or Fearn.” (Id. ii. 1.) The ashes of fern, which grew abundantly in Tuscany, were also used by the Venetians. (Neri, op. cit., chap, v.) “Aisschen of feme.” , Chaucer, Squyeres Tale, Pt. I. 246Google Scholar.

^{page 103 note b} The potash of commerce is purer than the crude ash, but nevertheless before being used in modern glass-works is purified by dissolving in warm water, and, when cold, drawing off the clear solution, and; evaporating to dryness.

^{page 103 note c} , Gmelin, Handbuch der Chemie, Cavendish Soc. Edit. iii. 18, 78, 73.Google Scholar

^{page 103 note d} Pliny mentions specially that white sand,“passing soft andtender, wau used by the Romans (Naturall Historic, , Holland's transl. 1601. xxxv. 26).Google Scholar The natural purity of the sands of Murano was one of the secrets of the success of the Venetians. A good idea of the importance attached at present to the purity of this chief ingredient of glass, is that sand has actually been imported for glass-making from New South Wales; and the best sand of the Isle of Wight is not considered fit for use until it has been washed in eight waters, dried or burnt inan oven, and sifted through a lawn sieve (Pellatt, Apsley, op. cit. p. 36)Google Scholar; or quartz-sand is treated with hydrochloric acid, to free it from adhering traces of iron.

^{page 104 note a} Even to this day sand taken from the bed of the Tyne is used at Newcastle (Muspratt, Applied Chemistry, ii. 203), probably traditionally representing that first used by the Gallic glass-makers brought over by Benedict Biscop. Theophilus, in the second book of his Diversarum Artium Scheduler, which is a complete system of glass-making as practised generally in the middle ages, lays no stress whatever on the choice of sand, directing simply that it shall be taken out of water (what water not specified), and free from earth and stones. (Tollens …. sabuli diligenter de terra et lapidibus purgati, quod de aqua tuleris, cap. iv). The idea was in fact that any natural substance whatsoever could be made into glass, provided a suitable flux and strong enough heat were applied. “Vitrum omnium extremum est, ac post judicium quicquid sub firmamentum comprehensum est, omne in vitrum divina ordinatione convertetur.” (Magistri Joan. Isaaci Hollandi, Opera Mineralia, ii. 86.)

^{page 104 note b} Common chalk is not pure enough as a source for lime for modern glass, as it contains organic matter, which imparts a brownish tint Chalk from Dover is sent for even from the north of England (, Parnell. Applied Chemistry, ii. 27).Google Scholar

^{page 104 note c} On the presence of iron, lime, magnesia, and alumina in Gothic glass, see analyses by Müller, in Liebig and Koff's, Annual Report, iii. 455Google Scholar. Many analyses have shown the presence of iron, lime, and alumina in Roman glass.

^{page 104 note d} Inquiry, etc. edit. 1867, i. 24.

^{page 105 note a} “Le savon du verre.” Merret, 1662, sur le chap. xiii. “Savon de Verre.” Kunckel's note on ch. ix. of Neri, 1689.

^{page 105 note b} Chemical News, Aug. 16, 1862.

^{page 105 note c} Strabo not improbably refers to the use of manganese when he says that he was told by the glass-makers of Alexandria that there was a certain ναλιτνμ нνν in Egypt, without which the costlier and better kinds of glass could not be made. (Geograph. xvi. ii. 25.) Pliny certainly speaks directly of its use as follows: “Mox, ut est astuta et ingeniosa solertia, non fuit contenta nitrum miscuisse; coeptus addi et magnes lapis; quoniam in se liquorem vitri quoque, ut ferrum, trahere creditur.” (Nat. Hist. xxxvi. 66.) In early writers there is always confusion between magnet, manganese, and magnesia. The three bodies were indeed believed to be substantially the same; the first, or common kind (magnet), attracting iron; the second (manganese) attracting glass (out of sand, see Pliny, supra); and the third (magnesia) attracting flesh (placed dry upon the tongue the last stuck fast to it); in accordance with the view that every material thing in nature had a magnet of its own (if only it could be discovered, which was one of the great problems of the Middle Ages). Manganese and magnet were, moreover, extremely similar in appearance; indeed the two were not finally distinguished until the last century. Which of the three substances is intended, in any given case, can therefore only be ascertained by the context, or circumstances. In this instance we know at once that it was manganese, because neither of the other two substances wouldproduce the effect described. In another passage (op. cit. xxxvi. 25), the five then accepted different kinds of magnet are enumerated, one of them only attracting iron and the rest not; and in yet another (op. cit. xxxiv. 42), speaking of a kind found in Cantabria, he says that he did not know whether it was useful in glass-making, because no one had ever tried it. The use of manganese at that time must therefore have been common, as Beckman remarks, since it occurred so readily to Pliny in this connection. S. Isidore of Seville (op. cit. xvi. 4, A.D. 570–636), evidently quotes the first of the above passages from Pliny, when he says, describing the manufacture of glass, “Magnes….liquorem quoque vitri ut ferrum trahere creditur;” and Vincent of Beauvais (Spec. Nat. viii. 19, A.D. 1250), repeats the same from S. Isidore. Beckman refers to Roger Bacon and Basil Valentine as further authorities; but, though both writers appear to refer to manganese, I have not been able to discover any passage in which they speak distinctly of its use for purifying glass. Albertus Magnus, however, (b. 1193, d. 1280. De Mirabilibus Mundi, and De Secretis Mulierum, etc., Amsterdam, 1702–12, p. 75) does so: “Magnes trahit ferrum, carabe trahit paleam, et quidam alius lapis trahit vitrum.” Also in his book De Mineralibus, II. ii. 11, Opera, Lugduni, 1651, Part II. p. 234: “Magnesia, quern quidam magnosiam vocant, lapis est niger, quo frequentur utuntur vitrarii; hie lapis distillat et fluit in magno et forti igne, et non aliter; et tune immixtus vitro ad puritatem vitri deducit substantiam.” Mr. Nesbitt quotes a valuable receipt for making glass from an Italian MS. dating from the year 1443, lately published by Milanese (in Disp. li. of Scelta di Curiosita Letterarie Inedite Eare): 200 lbs. of soda, 40 lbs. of tartar, 150 lbs. of quartz pebbles, and 7 oz. of manganese. Baptista Porta (b. 1445, d. 1519), remarks on the use of manganese in the manufacture of artificial amethysts (Magics Nat. VI. vi. 4), black smalt (VI. viii. 3), and amethyst smalt (VI. viii. 9); but adds, “Utimur autem magnete in vitro conficiendo,” and then quotes the well-known passage from Pliny (VII. lvi.) Agricola (b. 1494, d. 1555. Georgii Agricolse De He Metallica, Basilise Helvet. 1621, p. 470), speaks thus distinctly of its use:” Verum sabuli vel arena?, ex lapidibus liquescentibus confect portiones duse cum nitri vel salis fossilis, aut ex herba salsa facti una commisceantur: ad quas adjiciatur minuta magnetis particula; certe singularis ilia vis nostris etiam tetnporibus eeque ac priscis ita in se liquorem vitri trahere creditur, ut ad se ferrum allicit; tractum aut purgat, et ex viridi vel luteo candidum facit; sed magnetem postea ignis consumit. “Cesalpinus (b. 1519, d. 1603, De Metallicis libri tres, Andrea Csesalpino Aretino, Noribergse, 1602, p. 152) marks the distinction between manganese and magnet:” Hoc genus hodie vulgo vocatur manganese, ab Alberto (as above) magnesia; lapis est niger magneti similis quout utuntur vitrearii. Si enim modicum ejus vitro admisceatur, illud purgat ab alienis coloribus, et ciarius reddit; si vero amplius tingit colore purpureo.” Whilst upon the subject it may not be altogether uninteresting to give some further references, though they are to later writers. Thus Cardan (b. ] 501, d. 1576. Hieronymi Cardani De subtilitate, v. Opera, Lugduni, 1663, iii. 451,447): “Constat vitrum ex tribus lapidibus scilicet lucidis, vel arena, sale chali, et sydera…sydera, quam manganensem Itali vocant, terra est repurgando vitro aptissima.” Mercati (b. 1541, d. 1593, Metallotheca, p. 148) says: “Manganese…. cum figulis turn vitrariis usum praebet; nam vitrum tingit purpureo colore ipsumque depurat, adeo ut si viride vel flavum suapte natura sit, eius mistione albescat, puriusque efficiatur.” Leo-nardus Camillus (Speculum Lapidum, i. 9, p. 31): “Quidam lapis, ex quo nostri vitrarii vasa dealbant.” (Id. ii. 7, p. 71): “Alabandicus niger in pupureum vergens lapis est a loco nomen sumens suae primæ. inventionis; ab igne colliquatur ac funditur more metalli; utilis ad vitrariam artem cum vitrum olarificet et albefacit. Keperitur inmultis Italiae locis, et a vitrariis mangadesum dicitur.” (Id. p. 132): “Magnasia sive Magnosia ex nigro colore in commoditate ad vitrariam artem. Idem quod Alabandicum.” Van Helmont (b. 1577, d. 1644. Opera, Lugduni, 1667, 472, sec. 143): “Magnes… minutulumenim ejus fragmentum, in massam vitream injectum, dum coquitur, é viridi vel luteo candidum efficit.” Kircher (b. 1601, d. 1680. De Arte Magnetica, 1654, p. 75): “In vitro conficiendo insignis usus est magnetis … purgat, et ita vitrum ex virido et luteo candidum facit, et crystallinum, magnes vero ab igne postea consumitur.” Sir Thomas Brown (1646, Vulgar Errors, ii. 3): “True it is that in the making of glass it hath been an ancient practice to cast in pieces of loadstone.” Neri (1612) speaks of the use of manganese for decolorizing glass as an established practice (Ch. ix. x. xiii); as do also his commentators, Merret (1662), and Kunckel (1689). Without such references the use of manganese for purifying Gothic glass might be proved, it might at first sight be thought, by the analyses which indicate its presence, the accuracy of which is not questioned. C. H. Clarke, Esq., F.S.A., however, in the discussion which followed the reading of this essay, ingeniously suggested that the discovery of manganese by analysis was not a sufficient proof of its haying been used with this intention, and that its presence might be accounted for by beechwood-ashes (which contain manganese) having been used as described by Theophilus. Mr. Clarke stated further that he had seen a specimen of glass made from beechwood-ashes, which was of a delicate pink colour. But manganese occurs in Gothic glass in greater quantity than can be accounted for by its having been conveyed, accidentally, in the ashes of which the glass was made; and, though it may be possible to communicate a pink tinge to glass made of pure sand by means of the manganese contained in the ashes of beechwood, it is not possible to do so if the glass be made of a ferruginous sand such as was alone used in the Middle Ages (Ex. 91–94).

^{page 106 note a} Pellatt, Apsley, op. cit. p. 32.Google Scholar

^{page 107 note a} Lehmann is thus incorrect in stating that cobalt ore was first used to tinge glass blue by Christopher Schurer, a glass-maker at Platten, about the year 1540; and Klaproth, Gmelin (both of whom analysed specimens), Beckman, and other writers, in attributing the colour of Gothic blue glass to iron instead of cobalt. The fact is that all old glass, of whatever colour, contains iron, and the cobalt is so powerful a pigment that one thousandth part only will stain glass a deep blue colour, and one twenty thousandth part communicate a perceptible tint (, Knapp, op. cit. ii. 120Google Scholar , note). Its presence therefore may easily be overlooked. Thus Parnell, writing in 1844, remarks— “The presence of oxide of cobalt has never been detected in any specimens of ancient blue glass” (Applied Chemistry, ii. 84Google Scholar). See, however, further on this subject in Winston (Inquiry, etc. i. 363, note; and Memoirs, p. 182); from which it appears that cobalt was first found in Gothic glass in 1850 by Mr. Medlock. Neither Mr. Winston nor Mr. Medlock, however, appear to have suspected that the native ore was used; and yet it seems clear to me that that is what was meant by the zaffiro, zafiro, zaffera, zaphara, saphra, etc. of the middle ages. Zaffre, ωαπøειþοοσ, safirus, sapphire; hence the sapphires put into the Abbe Suger's glass at S. Denis, that have excited so much wonder, like the mythic silver in church bells, for sapphires could not have communicated any tint. Another curious corruption or mistranslation of the word Zaphara occurs in the English edition (London, 1658, p. 181) of Baptista Porta; in which we have saffron.

^{page 108 note a} Baptists Porta, Mag. Nat. vi. iv. 2, Crocumferri conficiendi.

^{page 108 note b} Knapp, op. cit. ii. 27. “Good results depend upon an intense and continuous fusion .…the heat can scarcely be too great; driven snow is not whiter than the burning coal in the centre of the furnace, when it has reached its maximum of intensity.” (Pellatt, Apsley, op. cit. pp. 39–49).Google Scholar

^{page 108 note c} , Theophili, op. cit. ii. 4, 5, 23Google Scholar . Coal was not used until the year 1635, when Sir Eobert Mansell, knight, obtained a monopoly for making flint glass, in consideration of his being the first to employ pitcoal instead of wood in his furnaces. The kind of wood, and the importance of selecting that which is suitable, with many interesting details, will be found inNeri (1612), ch. viii. ix. and in the note by Merret (1662) on ch.ix.

^{page 108 note d} It is extremely difficult to understand quite clearly the descriptions either of , Theophilus (op. cit. ii. 1, 5)Google Scholar , or of , Heraclius (op. cit. iii. 7)Google Scholar ; but the above appears to be the substance of it so far as the present inquiry is concerned.

^{page 109 note a} Sir Wilkinson, J. G., op. cit. iii. 338.Google Scholar

^{page 109 note b} Spec. Doct. 1056.

^{page 109 note c} The temperature at the bottom of the pot is about one-fourth lower than it is at the top (, Knapp, op. cit. ii. 33).Google Scholar

^{page 109 note d} Faraday, in his experiments on optical glass (Philosopli. Trans. 1830), found on examining pots containing not more than six inches in depth of glass, made from the usual materials and retained at a full red heat for twenty-four hours, that the lower layers remained denser in the mean proportion of 4-10 to 3-43, and that great variations occurred in the density of glass taken even from the same horizontal layer.

^{page 109 note e} , Knapp, op. cit. ii. 35Google Scholar . See also pp. 104, 105; and , Faraday, Philosoph. Trans. 1830Google Scholar.

^{page 109 note f} But not all. Even at the present day, in house-windows glazed with flashed glass, concentric lines often occur which give an enormous distortion to objects seen, from the inside; and though, in spread glass, there is no visible distortion, the surface, seen from the outside, is full of undulations. Still, blown glass, of whatever kind, is always much freer from imperfections than that which, even out of the same pot, has been cast.

^{page 110 note a} In making modern window glass, a mass of about nine pounds of melted metal, at the end of a blowpipe, is whisked out into a circular sheet fifty or sixty inches in diameter.

^{page 110 note b} Op. cit. i. 6, 9.

^{page 111 note a} Winston is correct in stating that the art of flashing glass was known at least as early as the fifteenth century (Inquiry, i. 23, 162). He mentions, in particular, two bull's eyes in situ amongst the painted glass in Mells church, Somersetshire, which belongs to the latter half of the fifteenth century; and there are six, filling in the top foliations of the tracery lights of a window which retains its original glazing, of the latter part of the fifteenth century, in the north aisle of the nave of Nostell Priory church. It is certain, however, that until the next century the process was not brought to such perfection as to occasion any essential difference in texture.

^{page 111 note b} The analogy between Gothic glass and certain natural products will be referred to again further on. That the beauty of many precious stones is greatly due to their want of homogeneity, and consequent effect on light, is well known. Opal (Ex. 118) and lapis lazuli (Ex. 119) may be mentioned, in addition to the above.

^{page 112 note a} , Winston, Memoirs, p. 180Google Scholar . An illustration of the difficulty, or perhaps impossibility, of making perfectly transparent Gothic glass, is the enormous value that was attached to certain glass vesels preserved in some of the sacristies abroad. These, from their perfect manufacture, were not suspected to be glass, but believed to be precious stones. The Sacro Catino at Genoa, for instance, was believed, as already stated, to be an emerald; Theodolinda's cup at Monza, a sapphire; and many of the ancient reliquaries of fine crystalline glass mounted in gold were thought to be crystal.

^{page 113 note a} Liebig and Kopp's Annual Report on Chemistry and the Allied Sciences, ii. 308. When large masses of glass are allowed to cool slowly in the melting-pots, beautiful crystalline effects may frequently be observed (Ex. 128, 129, 130, 131). Dumas and Kersten analysed specimens both of the crystalline and vitreous portions of similar glass, with the following result:—

Both portions, therefore, are distinct chemical compounds (, Knapp, op. cit. ii. 12Google Scholar . See further , Dumas, Traité de Chimie appliquée aux Arts, ii. 552Google Scholar ; Peligot, Sur la Cristallization du Verre, Comptes Eendus de l'Académie des Sciences, 1874, pt. i. p. 386).

^{page 114 note a} , Knapp, op. cit. ii. 3Google Scholar . See also , Gmelin, op. cit. iii. 378Google Scholar . “The presence of too much alumina produces in the glass a tendency to crystallize.”

^{page 114 note b} Op. cit. ii. 1-8; confirmed by , Heraclius, op. cit. iii. 7.Google Scholar

^{page 115 note a} The term white glass indicates, not that which is colourless, but that which is not intentionally stained with any colour. The Gothic white glass varied from bluish-green to green, sea-green, greenish-yellow, and yellow; nevertheless, the term white is justified by ordinary usage and by analogy: thus, for instance, we call green or yellow grapes white, in order to distinguish them from purple.

^{page 115 note b} Op. cit. ii. 112.

Journal de Chimie Médicale, Paris, ix. 277.Google Scholar

^{page 116 note a} “Handbuch der Chemie,” Cavendish Soc. edit. i. 170; and iv. 245.

^{page 117 note a} The exquisite pink glass of the fifteenth century, one of the most brilliant, but most delicate of colours, is best represented by the blossom of the heath—the five-leaved heath (Erica cinered), as distinguished from the ling (Calluna vulgaris), or cross-leaved heath (Erica tetralix).

^{page 118 note a} Professor , Church, Colour, p. 105Google Scholar . All that is said, in this excellent little handbook, on the colours of precious stones and of glass is admirable.

^{page 119 note a} “The foxglove blossom—a third part bud, a third part past, a third part in full bloom—is a type of the life of this world, and in all things that live there are certain irregularities and deficiencies which are not only signs of life, but sources of beauty.”—, Ruskin, Stones of Venice, ii. 6.Google Scholar

^{page 120 note a} Like the colours in a Turkey carpet, or, in Nature, such combinations as, for instance, the blossom and foliage of the flax, or the bright green foliage of a lemon-tree, loaded with golden fruit, and azure sky showing through the branches.

^{page 120 note b} The same applies to much of the modern imitation old Venetian glass, the colours—rose-pink, paleblue, opal, etc.—being flimsy, crude, or staring, for the same reason as those of imitation Gothic.

^{page 120 note c} On the small scale, and imitative specially of the decay of crystalline glass, an “iridescent glass” for inkstands, vases, etc. has just been brought out and become extremely popular. The coloration, however, instead of being intensely deep and rich in tone, infinitely varied, and partially and fitfully distributed, is extremely thin and flimsy in appearance, but little changeable, and distributed uniformly with the most artificial neatness.

^{page 120 note d} The modes of “antiquating,” mentioned above, are resorted to as much to hide the flimsiness and poverty of the modern material as to “obtain” the effect of age. The glass, whether in its original or altered state, when tested by Winston's canon, is found wanting. When held at arm's length from the eye, before being “antiquated,” it permits an object to be distinctly seen at many yards' distance; while, after being “antiquated,” an object that is more than an inch distant cannot be seen at all. Of the two methods the latter is the worse, because, in addition to rendering the glass opaque, it gives it a peculiarly dark and heavy appearance.

^{page 121 note a} Paracelsus, De Generatione Rerum; with which compare Plato, Republic, bk. x. Steph. ii. 602.

^{page 121 note b} “It must not be forgotten that even pure water dissolves very appreciable quantities of glass. The influence of the matter dissolved from the flasks, etc., used in the operations, is too frequently lost sight of in quantitative analysis. There is no doubt that the results are affected to a greater degree than is usually supposed.” (Thorpe, Quantitative Analysis, p. 47.)

^{page 121 note c} , Gmelin, Handbook of Chemistry, iii. 383.Google Scholar

^{page 121 note d} “Observatum est … ferrum ad austrum expositum citius rubiginem contrahere, ad septentrionem tardius, ut in bacillis illis ferreis, aut cratibus, quae ad fenestras apponuntur.” (, Bacon, Hist. Vitce te Mortis, i. 4.)Google Scholar

^{page 121 note e} Not generally, however, in old churches if un- “restored,” or in new ones if properly ventilated.

^{page 122 note a} , Bacon, loc. cit.Google Scholar

^{page 123 note a} , Gmelin, op. cit. iii. 383, 384.Google Scholar

^{page 124 note a} Inquiry, etc. i. 24.

^{page 125 note a} The yellow stain, it will be remembered, is ordinarily applied on the otitside of the pane, but is invisible except from the inside.

^{page 126 note a} The outer portion of such shell consists of crowded polygonal prisms placed perpendicularly more or less obliquely to the surface, of a texture which we can demonstrate by the polariscope to be extremely variable (Ex. 144). On exposure to the atmosphere, the softer prisms are the first to decay, leaving the harder portions intact. Other shells, when exposed to the weather, illustrate other forms of decay; as when, for instance, multitudinous parallel layers or lamellas are dissected out by the decay of a previously smooth and unbroken surface, leaving sharp edges standing out free, and resisting the action of the atmosphere for a longer period (Ex. 145). This mode of decay rudely resembles that of the glass which, being affected with the first form of granular decay, causes sub-iridescence as explained above.

^{page 127 note a} That the particles in unannealed glass are in an irregular state, is beautifully demonstrated by the polariscope. Place a piece of glass, an ordinary microscope slide for instance, in a polariscope furnished with a selenite plate, and no change will be observed; but remove the glass, heat it nearly to melting, then suddenly cool it so as to render it unannealed, and on replacing it in the polariscope a most beautiful play of colours, indicating physical inequality of texture, will be observed.

^{page 127 note b} In a somewhat similar manner, if fluoric acid be applied to a portion of the surface of a pane of Gothic glass, it becomes, when washed and dried, perfectly white. The acid dissolves out the silica, alumina, soda, potash, and iron, but leaves the lime and magnesia in the form of insoluble fluoride (Ex. 146).

^{page 127 note c} The statement of Mr. Pellatt, Apsley (op. cit. p. 138)Google Scholar , that iron in glass preserves it from decay, is incorrect. It is. cceteris paribus, exactly the reverse, just as preponderance of lead, in flint glass, induces decay; lenses of flint glass being more prone to “mildew” than those of crown glass, and those now made, especially by inferior houses, than those made formerly, the labour for cheapness and excessive brilliance inducing the addition of too much lead, whereby the glass is rendered softer and more prone to decay.

^{page 128 note a} The rusting of an iron rod splitting the stone into which it is fixed, and the hydration of lime in badly tempered mortar throwing down a wall built with it, are familiar examples of this kind of action on a large scale.

^{page 128 note b} The black dentritic arborescent markings in chalk and flint are oxide of manganese (, Mantell, Geolog. Excursions round the Isle of Wight, p. 130)Google Scholar ; the supposed vegetable structures in agates (Ex. 148), are oxide of iron (Griffith and Henfrey, Micrographic Diet., s. v.) Mica also contains similar deposits (Ex. 149).

^{page 128 note c} It is to get rid of them that the scales of decomposing glass are boiled in acid (Ex. 86).

^{page 128 note d} The extraordinary cementing power of iron may be seen sometimes on picking up a rusty nail on the sea-shore. With it, firmly attached, will often come up a lump of conglomerate weighing several pounds, which, when dry, becomes so hard that, if struck with a hammer, the pebbles will break rather than leave the cement which binds them.

^{page 129 note a} Optics, ii. 2.

^{page 130 note a} A glassy mineral of white pearly lustre, found in the trap-rocks of Skye, etc. consisting of the silicates of lime and potash.

^{page 130 note b} A mineral in the form of white flexible threads, from Sardinia, consisting of the silicates of lime, magnesia, iron, and manganese or soda.

^{page 130 note c} How far the alkalies are removed in decayed glass is shown in an interesting manner by the following analyses (A) of the unaltered inner portion, and (B) of altered exterior coating of ancient glass dug up near Eome:—

And from an analysis by C. W. Bingley, Esq. Ph.D. F.C.S. it appears that whereas the unaltered inner portion of glass found in the lake at Walton Hall, near Wakefield, consisted of silicate of potash, with very slight traces of lime and iron, the scales of the exterior or decomposed portion were found to consist of silicate of lime, associated with iron, but no potash or soda. (British Association Report, 1859, p. 45.)

^{page 131 note a} Dumas, Traité de Chimie appliquée aux Arts, ii. 575, 576. The bottles at first made were lighter and otherwise superior to those in common use, but the process had to be discontinued because of the difficulty of getting, 1. Minerals of uniform composition; and 2. Customers who would be satisfied with “bottles that were not uniformly of the same appearance. Further experiments were made by M. Alliot, who found basaltic earth exceedingly well qualified, both by itself and combined with other substances, for fusion into glass. Messrs. Chance, of Birmingham, have also utilized the vitreous slag of iron foundries.

^{page 131 note b} A mixture of silicates of the alkalies, lime, magnesia, alumina, and iron.

^{page 131 note c} , Lyell, Principles of Geology, p. 249.Google Scholar

^{page 131 note d} Silicate of magnesia, lime, alumina, potash, and soda.

^{page 131 note e} , Phillips, Geology, p. 469.Google Scholar

^{page 132 note a} The various clays, so extensively used for all kinds of brickmaking and pottery, are the product of such decomposition. The following analyses (A) of Felspar, and (B) of Clay, dried at 212°, will serve for illustration:—

but both the felspars, etc., and the clays differ in composition, and I cannot lay my hand on an analysis of a specimen of felspar and of clay formed from the decomposition of the same rock. In red clay the lime is as much as 1-5 per cent., magnesia 2 per cent., and iron 8 per cent. (See, on this subject, a valuable summary in , Knapp, op. cit. ii. 202.)Google Scholar

^{page 132 note b} Proc. Soc. Ant, 2 S. iv. 284.

^{page 132 note c} Id. v. 114. The Cornwall bottle, mentioned at p. 135, having been built into the wall of the church, embedded in the east wall behind the altar” (letter from Mr.White to the -writer), belongs to a different category, and, like the glass vessels found of late in the altars of churches on the Ehine, need not now be considered.

^{page 133 note a} It has been suggested by Mr. J. T. Micklethwaite, F.S.A., and I think with probability, that the bottles thus buried in consecrated ground may have contained—not “St. Katharines oyle,” or the like, but Aquam a renibus humanis secretam, and been charms against witchcraft, or for the cure of certain diseases. It was com mon enough in the seventeenth century for any one who had a weakness to bore a hole in an oak tree, and fill it with cuttings of hair and parings of nail, under the impression that the disease of the afflicted person would be attracted by the strength of the tree to itself; or to pare the nails of the fingers and toes of the person, tie the parings in a rag cut from his clothes, and bury them in some secret and unknown place (, Pettigrew, Medical Superstitions, p. 72Google Scholar ; , Kircher, De Arte Magnetica, 1654, iii. 2)Google Scholar ; or bury the water in an ants nest ( , Ennemoser, Hist.Magic, Howitt's edit. ii. 209Google Scholar ; , Pettigrew, op. cit., p. 75)Google Scholar , or dunghill (id. p. 76); special care being taken by any one accidentally finding the same not to touch it, lest he should receive the buried weakness (Ennemoser, Pettigrew, etc.). When the patient was suffering from witchcraft, the water was corked up in a bottle with pins, needles, and nails, and put before a fire (Brand, Pop. Antiq. Bonn's edit, iii. 13), or up the chimney, or buried at the doorstep, or in the “wall-roots” of the house in which the patient resided. Numerous instances of the practice of these superstitions even at the present day, in remote country districts, have come within my own cognizance, and others have been related to me by those in whose experience they have occurred. Mr. Peacock has found a dozen or more such bottles in the “wall-roots” of cottages pulled down on his estate at Bottesford; and he says that in North Lincolnshire, and elsewhere, the charm is still practised as a remedy against witchcraft. Professor Stephens, of Copenhagen, informs me further that such bottles are not unfrequently found in Denmark, usually very carefully fastened, fi not sealed; that they are usually of late date, of the seventeenth or eighteenth century; that they occur always in out-of-the-way places; and that he believes them to have been so buried in connection with popular and superstitious sympathetic and magical medicine. From the Saxon “Leechdoms,” edited by the lamented Eev. 0. Cockayne, it would appear that the burying of charms in “wall-roots” was familiar even to our Saxon forefathers (i. 329); who also made drinks for fiend-sick men, to be drunk out of church bells (ii. 137). The use of holy water, holy oil, and so forth, to expel demons, was also very ancient; and Jerome Mengs, in his Flagellum Desmonum, speaks familiarly of the use of “Keliquite sanctorum, lignum crucis, et similia,” for a like purpose. The idea of the sacredness of wedding-rings, churchyards, etc., continued to a late period, and in the seventeenth century became mixed up with the belief in “sympathy,” “transplantation,” and the like. Later still, the idea of a sacred place being necessary was lost, and it was sufficient if it were a healthy one, or even a secret one (not likely to be disturbed by one's enemies), in which, the weakness of the afflicted party might quietly be buried, and thus got rid of for ever. The belief that decay and destruction were induced more rapidly by the soil of a cemetery than by that which was pure and uncontaminated should, however, be noted in passing. (“Cemiteria, in quibus quotidie fiunt sepulturse, ubi terra cadaver aliquod recens impositum consumit longe citius quam terra pura.” Bacon, Sylva Sylvarum, 330; with which compare the burial of the water of a sick man in an ants' nest, or dunghill, noted above). “Humana excrementa etiam post ejectionem seculis anteactis credebantur potentiam sympatheticam nihilominus in corpus emittentis retinere, heneficium vi quadam niystica recepturi, si, exempli gratis, solum sacratum illis imponeretur, vel aliter noxam, ut e verbis sequentibus satis patet. “Si quis ad ostium tuum cacaverit. idque prohibere intendas, ignem ferri recenti excremento superstruito; mox per magnetismum natibus scabiosus cacator fiet: igne videlicet torrente excrementum et tosturse acrimoniam quasi dorso magnetico, in anum impudentem propellendo.” (Helmont, Van, Be Magnetica Vulnerum Curatione, § 21Google Scholar . Idem remedium apud Kenelmum Digbeium invenitur, op. cit. 126.) On the other hand, country people were believed to have sounder constitutions and to live more healthily because they were able to commit their excreta “to the earth, most commonly amongst wholsome herbs, and so by meanes of an occult Transplantation lead their lives more free from diseases.” (Medicina Magica tamen Physica, or a methodical Tractate on Diastatical Physick, 1656, chap, xxvi.) The reason why the water was specially chosen for experimenting with, and for making magical cures, insomuch that a grievous disease of the whole body is no way better cured than by it, was because “it hath no obscure consent with the whole body,” being derived from all parts of it. (Id. chap, xxvii.) We have thus sufficient evidence of the burial, for the production of magical cures, of such bottles in wall-roots and other places, for instance churchyards, in which it was presumed the “buried weakness” would either on the one hand Bpeedily decay, or on the other receive and transmit a blessing; and have formed some idea also of the light i n which the subject presenteditself to our forefathers. Lectorem denique animadvertere velim Pharmacopolae Lutterworthensis testimonium, cui ampulla vitrea ihi inventa olei origani odorem referre videbatur. Hoc enim prsecipue notandum existimo, quia nullum pharmacorum quse noverim putrescentem urinam mani festins olet.

^{page 134 note a} , Winston, Memoirs illustrative of the Art of Glass-Painting, p. 44.Google Scholar

^{page 135 note a} This term is not used here in the loose sense in which it is too often applied to almost all old glass as compared with modern, but to denote an effect of transmitted light which does, strictly and accurately speaking, very closely indeed, resemble that of light reflected from a plate of burnished silver, or from a pearl.

^{page 137 note a} Under this now become offensive term I do not of course include the ingenious and intelligent repairer or preserver. Where the lead of an old window has become defective and the glass loose and in danger, I should be the last to otherwise than sincerely sympathize with its being re-leaded and properly preserved.

^{page 137 note b} See a report by the present writer, in Athenseum, 29 March, 1873.

^{page 138 note a} Some years ago it was warmly discussed whether the Fairford windows had not been injured by washing. There is no question that many windows in many churches have been so injured. In the last century, especially, it was thought only right that the windows should be washed regularly. The following entries are from the Wakefield Churchwardens' Accounts:— “1634. For dressing of the leads and the Church windowes.” “1619. Paide for sweepeing the church walles, wyndowes, and the leads dyvers tymes, vijs. iijd.” “1742. Pd. Thos. Moyl Apprene for cleaning ye Church Windows, 2s.” “1768, Eobert Newman W^te wash'g windows, Is.”

^{page 139 note a} It is not breath alone which thus condenses on the inside of windows. Mr. Hughes, of London, was the first to point out to me the sooty smell and treacly consistence of the condensed vapour on windows in modern churches. He tells me that on more than one occasion he has been sent for to see windows in the condition described above, and that, on inserting a ventilator near the roof at each end of the building, the damp has disappeared immediately, and not returned.

^{page 142 note a} Now forming part of the collection bequeathed by Mr. Henderson to the British Museum.

^{page 144 note a} “The aqueous solution of potash is kept in bottles with glass or cork stoppers. In either case none of the solution should touch the stopper; for those of glass become in a short time so strongly cemented in that they cannot again be withdrawn; and corks corrode and impart a brown colour to the liquid.” (, Gmelin, Handbuch, etc. iii. 14.)Google Scholar